Paper tape element of the joint sealing assembly of walls composed of wallboard



June 12, 1962 H. L. cowAN 3,038,277

- PAPER TAPE ELEMENT OF THE JOINT SEALING ASSEMBLY OF WALLS COMPOSED 0 ALLBOARD Filed Nov. 6, 9

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I N VEN TOR HaroJdL. C0 Wan,

ATTORNEY that 3,3,277 Patented June 12, 1962 his (3F THE JOINT SEALENG ASSEMBLY OF WALLS CGMPOSED F WALL- 3 03 PAPER TAPE ELEMEIQT In the construction of walls formed of sections or units of wallboard the established practice and structure for sealing the joints between adjacent boards and for presenting a smooth surface in uninterrupted continuity with the surface of the wall to which a decorative coating of paper or paint may be applied, is as follows: The longitudinal edges of the units are formed on one face with shallow recesses somewhat more than an inch in width and of the order of one-thirty-second of an inch in depth which, with the units abutted, provide a channel somewhat more than two inches in width and continuous with the lengths of the board as arranged either vertically or horizontally. The channel is sealed by suitable cement which, in respect to expansion and contraction, is ad versely affected by atmospheric moisture conditions. Unless otherwise compensated the recurrent cycles of expansion and contraction will develop through the area of the cement a multiplicity of small cracks extending in various directions. To counteract this tendency a reinforcing layer of stout paper, e.g. having a width of two inches and a thickness of the order of .009 inch, has been used for many years. This paper layer, generally called a tape, is pressed upon the plastic cement for the full length of the joint and is formed with circular openings having a diameter of three sixty-fourths of an inch and arranged in transverse rows with four openings in each row, the rows being about five-sixteenths inch from one another and the cement extending through the openings whereby the paper is spot-keyed to the cement. When the cement has dried a beddingcoat consisting of cement of the same character is then applied with pressure to the paper and is feathered out for a few inches on each side of the channel. When the bedding coat has dried its ex posed surface is sanded to present a smooth surface in level and uninterrupted continuity with the wallboard surface.

In the practice and structure above described, the paper reinforcement although counteracting the cracking tendency above noted has itself resulted in a substantial and long known disadvantage, namely the development of an unsightlycrack extending longitudinally along the joint seal. Sundry structural features and practices to overcome this disadvantage have been proposed, all of which have the substantial objections of increasing the cost of material and work and in some instances of sacrificing the advantageous feature of spot-keying the tape to the base layer of cement. In the construction of the seal the tape, which is much stronger than the cement, absorbs moisture from the plastic base layer with resultant expansion. When the base layer dries as is required for the application of the bedding coat, the tape also dries with resultant shrinkage. When the bedding coat is applied the tape again absorbs moisture and expands and when the bedding coat dries the tape also dries and again shrinks. During the life of the wall, these cycles of alternating expansion and shrinkage repeatedly recur due to the varying humidity conditions of the air, the cement and the wall decoration being porous and moisture from the air in varying degrees being absorbed by the cement and the tape. Since the tape as spot-keyed to the layers of cement in a unit of time expands and shrinks to a substantially greater extent than the cement, expansible and contractile stresses are positively transmitted by the tape to the cement with resultant formation of air pockets or blisters under the tape which weaken it as a reinforcement of the seal and with resultant development over a period of time of a visual crack lengthwise of the sealing structure and which extends through the bedding layer, the tape and the base layer, the usual practice of eliminating these cracks by covering them over with an appropriate filling medium which of course must be unified in appearance with the surface decoration of the wallboard being merely a palliative and entailing considerable expense.

This invention relates to an improvement in the paper tape reinforcing element of the above described joint sealing assembly of walls composed of wallboard.

The object of the invention is to provide a paper tape reinforcing element having novel structural features by virtue of which and without changes in the process for the production of the element, without increase of the cost of the element, and without change in the established practice and structure for sealing the joints, the disadvantage above described will be overcome, that is to say in which the expansion and shrinkage of the paper tape element is substantially eliminated by reduction to a negligible degree such that no destructive expansible and contractile stresses are transmitted to the layers of cement and hence wherein the factors above explained which result in the development of a longitudinal crack lengthwise of the joint are eliminated. It follows that the wall will be permanently free from cracks along the joint sealing means.

In my effort to determine whether the development of longitudinal cracks in the joint seals could be overcome I concluded: (1) that by reason of the small areas of the circular openings in the tape, the correspondingly small cross section of the cement keys, and the greater strength of the tape, such keys did not oppose adequate resistance to the lateral and longitudinal expansion and shrinkage or contraction of the tape and hence that the tape in its expansion and contraction effected in corresponding degree the expansion and contraction of the layers of cement, such degree being greater per unit of time than the expansion and contraction of the cement under the same conditions but independently of the tape; (2) that making the circular openings of greater diameter or increasing the number of circular openings would not be a solution and would only weaken the tape and reduce its capacity as a reinforcement; and (3) that with the circular outline of the small openings there could be no adequate interruption of the paths of expansion and contraction of the tape and hence no provision of mutually opposing or counteracting features which would substantially eliminate the expansion and contraction of the tape per unit of time with the result of the elimination of destructive stresses in the tape and in the layers of cement.

On the basis of my analysis as set forth in the foregoing paragraph I have developed a tape characterized by transverse rows of slots in a symmetrically patterned arrangement with four slots in each row, wherein the slots in adjacent rows are in angular relation in the directions of their lineal extent, the area of each slot somewhat exceeds the area of each small circular opening of the tape heretofore used, the angular relation of the slots interrupts or localizes the paths of expansion and contraction whereby opposing factors of resistance to expansion and contraction are set up, a more equable and eflicient areal distribution is effected between the perforate and imperforate areas of the tape per unit of area encompassing adjacent rows of slots, and the expansion and contraction of the tape as a whole is reduced to a negligible, scarcely measurable, degree. As to their dimensions it is recommended that the slots should not appreciably exceed one-eighth by three sixty-fourths of an inch. The cement keys correspond in form and dimension to the slots and are stronger than the keys formed by the circular openings of the tape heretofore used, thereby to oppose greater resistance to the expansion and contraction of the tape. The pattern arrangement of the slots, their precise form and their angular relation are susceptible of sundry variations, any of which will produce the essential result of the substantial elimination of the overall expansion and contraction of the tape, the slot pattern arrangements herein shown being merely exemplary. It is to be noted that the principal factor in the development of cracks lengthwise of the sealing joint with the perforated tape heretofore used has been its lateral expansion and contraction. Comparative laboratory tests have established that the lateral expansion and contraction of the tape heretofore used is 1.6 percent of its width and that the tape of my invention as exemplified by the slot pattern arrangements herein shown has no appreciably measurable lateral expansion or contraction.

In the drawings:

FIGURE 1 is a transverse sectional view on an enlarged scale showing wallboard units in abutting relation and which may extend either vertically or horizontally and the sealing joint construction in which the tape of my invention is an element.

FIGURE 2 is an elevation on an enlarged scale of a fragment of the tape showing one pattern arrangement of the slots.

FIGURE 3 is a similar elevation showing another and equivalent pattern arrangement of the slots.

FIGURE 1 shows a wallboard joint seal in accordance with the established practice. The abutting wallboard units 1 may be of any desired construction and are secured to an adjacent stud by nails (not shown). Their adjoining side faces 2 provide the joint which is required to be sealed. Adjacent each of its faces 2 each unit 1 is formed on that side thereof to which decorative coating (paint or paper) is to be applied with a shallow recess 3, the adjacent recesses in the abutting relation of the units providing a channel 4 which of course is lineally coextensive with the units. In forming the seal a thin base layer of cement 5 is applied to the base of the channel. A strip of perforated tape 6 lineally co-extensive with the channel but of slightly less width, namely of the order of two inches in width as heretofore, is then imposed in symmetrical relation upon the base layer while it is plastic and by the application of appropriate pressure is embedded in the cement which of course fills the perforations of the tape and provides keys 7 for the mechanical connection of the tape throughout its length to the base layer, the cement as forced through the openings in the tape being smoothed down while still plastic and the tape absorbing moisture from the cement and expanding as previously explained. The cement is then allowed to dry, a drying period of twenty-four hours being recommended, and the tape dries with the cement and contracts as it dries, thereby returning to its original dimensions. When the cement and tape have dried, a bedding coat 8 of similar cement is applied over the tape. Two thin layers of the bedding coat are recommended, the first layer as it dries adhering to the tape and the keys 7 with which it becomes integrated and the second layer being applied after the first layer has dried, the layers being feathered out upon the wallboard for a few inches at each side of the channel. When the second layer has dried its exposed surface is sanded to make it smooth, level, and uninterruptedly continuous with the adjacent surface of the wallboard. In connection with the application of each layer of the bedding coat the tape absorbs moisture and expands and in connection with the drying of each layer of the bedding coat the tape also dries and contracts.

The tap 6 is much stronger than the cement and is provided as a reinforcement. As now advised the paper which has been used heretofore for the production of the tape is preferred (although paper of other specific description may be available), this paper being made by a well known bleached sulphate process which is combined with a chemical wet strength treatment in which the fibers, to adopt the term used in the trade, have a wild formation. In the construction of the joint the tape absorbs moisture directly from the cement as above explained and during the life of the joint it absorbs moisture from the air, such moisture permeating the porous cement and being carried by the cement to the tape by which it is absorbed with resultant expansion of the tape followed by its drying as the humidity in the air decreases.

The tape heretofore used has the small circular openings, the details of which have been sufficiently set forth in the foregoing description; and these openings which have been provided to effect the necessary keying of the tape to the cement layers are responsible, by reason of their specific form, dimensions, spacing and arrangement, for the development over a period of the life of the joint of the unsightly and damaging crack which extends lengthwise of the joint, the tape during such a period having many cycles of expansion and contraction.

Two forms of tape in accordance with the invention and which have equivalent merit, both having been given successful laboratory tests, are shown in FIGURES 2 and 3. Both forms are characterized by transverse rows of slots 9 in a symmetrically patterned arrangement where in the rows have a spacing of the order of one-fourth of an inch and the slots in adjacent rows are in angular relation, preferably of in the directions of their linear extent. Having regard to the width of the tape (two inches) the maximum transverse dimension of the perforate areas is of the order of one and three-sixteenth inches as heretofore and within this area four slots in each row in a symmetrically spaced arrangement are SUIIICICIII. The limitation of the slotted area provides imperforate longitudinal marginal portions 1! as heretofore of the order of three-eighths of an inch in transverse extent, these assuring adequate strength for the marginal embedment and preferably being skived on their under or inner faces to facilitate the embedment of the tape in the base layer. The slots 9 are of the order of one-eighth of an inch in lineal extent and three sixty-fourths of an inch in transverse extent. The transverse rows of slots are distinguished as X and Y and are arranged in alternate relation, viz X Y X Y X and so on throughout the length of the tape.

The slots 9 extend longitudinally and transversely of the tape and in respect to their directions of extent are distinguished as 9L and 9T.

In the form shown in FIGURE 2 the X rows of slots are each composed entirely of the slots 9L and the alternating Y rows of slots are each composed entirely of the slots 9T. The slots L are symmetrical in their mutual spacing but are not necessarily equidistantly spaced. Thus in the form shown in FIGURE 2 the slots 9L of each row are by preference arranged in pairs with an imperforate area 11 of greater width between the inner slots of the two pairs than the irnperforme area 12 between the two slots of a pair. The slots 9T of each Y row are preferably equidistantly spaced, the innermost slots 9T being aligned with imperforate areas 11 and similarly forming interruptions of their longitudinal continuity.

In the form shown in FIGURE 3 each X row of slots has endmost slots 9T and a pair of inwardly located slots 9L and each Y row of slots has endmost slots 9L and a pair of inwardly located slots 9T. In the X rows the slots may be substantially equidistantly spaced, and in the Y rows the two slots at the left are in substantial alignment with the outer vertical edges of the two X row slots at the left and the two slots at the right are in substantial alignment with the outer vertical edges of the two X row slots at the right.

In both forms colorable variations of the spacing of the slots in each of the two rows may be made without substantially impairing the overall patterns. In both forms the slots by virtue of their form and extent, their spacing and their angular relation in two adjacent rows provide keys of greater extent and strength for the connection of the tape to the cement layers and a more equable and efiicient areal distribution as between the perforate and imperforate areas of the tape per unit of overall area encompassing adjacent rows of slots, and so interrupt or localize the areas of expansion and contraction of the tape that opposing and neutralizing factors of resistance to expansion and contraction are set up with the results that the tape will not appreciably expand or contract during the construction of the joint seal and during the life of the wall.

As shown herein the joint seal is between adjacent units in coplanar relation. Where the walls composed of wallboard units extend at angles the joint seals, in accordance with the usual practice, may have an inside or outside corner arrangement. With this fact in mind the patterned arrangement of the slots should be such, as herein shown, that a narrow central longitudinal portion is uninterrupted whereby the tape may be folded when the seal is required at an inside or outside corner.

In the prior tape construction each hole, being of the dimension described, has an area in inches of .00172. Taking one inch as a unit of length of the tape encompassing three adjacent rows of holes with four holes to each row the combined area in inches of the twelve holes is .02064.

In the tape of the present invention each slot, being of the dimensions described, has an area in inches of .00586. Comparably taking one inch as a unit of length of the tape encompassing three adjacent rows of slots the combined area in inches of the twelve slots is 07032.

Thus in the tape of the invention the combined areas of the slots in three adjacent rows is somewhat more than three times greater than the combined areas of the Openings in three adjacent rows in the tape of the prior art. However, this increase in area of the slots of the invention, as compared to the circular openings of the tape of the prior art, is without any weakening effect because the angular relation of the slots in adjacent rows sets up the neutralizing stresses which prevent appreciable lateral contraction or expansion of the tape, all as above explained.

I claim:

1. A paper tape for use in joint sealing assemblies of wallboard units in abutting relation with adjoining faces providing the joint to be sealed which consists of a substantially parallel-edged strip of paper of the order of two inches in width and of a thickness of the order of .009 inch having a patterned arrangement of rows of rectangular slots with four slots in each row, each slot having dimensions of the order of one-eighth of an inch in lineal extent and three sixty-fourths of an inch in transverse extent, the rows of slots having a spacing of the order of one-fourth of an inch, the slots being arranged in corresponding relation in adjacent transverse rows with the adjacent slots in adjacent rows extending in substantially right angular mutual relation, the slots being provided within an area of the tape which leaves imperforate longitudinal marginal portions of the order of three-eighths of an inch in transverse extent.

2. A reinforcing tape as set forth in claim 1 wherein the slots in one row extend longitudinally and the slots in an adjacent row extend transversely.

3. A reinforcing tape as set forth in claim 1 wherein the slots in adjacent rows include slots which extend transversely and slots which extend longitudinally and the transverse and longitudinal slots of one row are adjacent the longitudinal and transverse slots of an adjacent row.

References Cited in the file of this patent UNITED STATES PATENTS 1,546,151 Strand et a1. July 14, 1925 2,038,173 Hathaway Apr. 21, 1936 2,667,822 Christman Feb. 2, 1954 

